The present invention relates to methods and apparatus for chemical reactions in heated reactors at negative pressure.
The publication WO 2010/083978 A2 describes a tube bundle reactor consisting of a plurality of heatable reactor tubes. The reactor has a homogenization plate with holes or channels for storing the reaction mixture before entry into the tube bundle. Each hole or each channel has the same dimensions.
EP 363 066 51 describes an inductively heatable reactor for fluid phase reaction processes, in particular for high-temperature pyrolysis of chlorodifluoromethane, which consists of a material block having a plurality of reactor tubes, where the material block can be inductively heated.
DE 27 12 728 A1 describes a tubular reactor for heating gases or vapours in which these gases or vapour are passed through a packing of electrically conducting bodies which are heated by electromagnetic induction.
DE 10 2007 034 715 A1 describes a method for producing hydrogen cyanide by the Andrussow method in which methane and ammonia are reacted at positive pressure to give hydrogen cyanide and water. For this purpose the reactor contains a gas supply line, a mixing layer, which can bring about a pressure drop, a catalyst layer and optionally a downstream heat exchanger for removing the heat.
US 2011/306788 describes a method for oxidizing organic molecules by heating the gas with the starting material in a catalyst-filled tube reactor. Various starting materials can be oxidized in this reactor, e.g. propylene, isobutylene, tert-butanol, methyl-tert-butylether, acrolein and methacrolein.
The publication U.S. Pat. No. 7,951,978 B2 relates to methods for producing acrolein from glycerin gas at pressures of 0.01 to 30 kPa by contact with a solid catalyst at temperatures of 200° C. to 550° C.
DS 3525749 A1 describes the BASF method for obtaining hydrocyanic acid by thermolysis of formamide at negative pressure.
WO 2009/062681 describes the production of hydrocyanic acid by catalytic dehydration (thermolysis) of gaseous formamide. The reactor for the dehydration has layers constructed in layer form with a plurality of reaction channels arranged in a cross manner, wherein the reactor has an inner surface which contains an iron fraction of more than 50 wt. %. The reaction channel has an average hydraulic diameter of 1 to 6 mm, where no additional catalysts and/or inserts are provided. The disadvantage of this design is that each channel is loaded with formamide in different quantities with the result that as a result of concentration differences, different products and by-products are formed.
The publication WO 2009/062897 describes a method for producing hydrocyanic acid by evaporating formamide in an evaporator and catalytic dehydration of the gaseous formamide. In this case, the evaporator was optimized for a performance of 10 to 2000 MW/m3.
DE 69215358 T2 describes an electrically heatable thermolysis reactor for the decomposition of exhaust gases at negative pressure.
A number of continuously operated chemical reactors for positive or negative pressure reactions are therefore known. However, usual pressure controls of conventional reactors for continuous operation have in common that in particular when using multiple reactors, a non-uniform introduction of the starting materials into the reactor can be the consequence. As a result, particularly in the case of short dwell times of continuous-flow reactors differences can occur in the reaction and the type of chemical reactions taking place to give by-products. This has a negative influence on the product quality and quantity since optimizations of quantities, flow rate, pressure and temperature parameters become difficult.